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Rare earth magnetic refrigeration materials

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Update time : 2017-12-29 09:59:31

Rare earth magnetic refrigeration materials

In the late 2020s, scientists discovered the phenomenon of rising temperatures in magnetic fields, known as magnetothermal effects. Subsequently, many scientists and engineers have carried out a lot of research and development work on materials, magnetic refrigeration technology and devices with magnetic thermal effect. So far, the low-temperature magnetic refrigeration devices under 20K have been used in some areas, and room temperature magnetic refrigeration technology is still in the research and development, and has not yet achieved the degree of practical application.

Magnetic refrigerating material is a material which has magnetic heat effect for magnetic refrigeration system. Magnetic refrigeration is first and foremost to magnets and magnetic field, the magnetic moment lined up according to the magnetic field direction, magnetic field, and then is removed to make the direction of the magnetic moment, absorbs heat from the surrounding magnets at this moment, through the heat to lower the temperature of the surrounding environment, to achieve the purpose of cooling. Magnetic refrigerating material is a kind of material which is used for magnetic heating effect. Magnetic cold material is the core part of magnetic refrigerating machine, which is the refrigerant or refrigerating quality of general appellation.

Low temperature superconducting technology is widely used, an urgent need to liquid helium cooling low temperature superconducting magnet, but the liquid helium is expensive, so hope can have the vaporization of helium gas and liquid helium liquefaction of small high efficiency machine. If the compressed air - expansion refrigerator is miniaturized, the compressor must be smaller, which will greatly reduce the efficiency of refrigeration. Therefore, in order to meet the needs of the liquid helium, people to accelerate the development of low temperature (4 ~ 20 k) magnetic refrigeration material and device, after years of efforts, the current low temperature magnetic refrigeration technology has reached the practical application. The magnetic refrigerating materials used in cryogenic magnetic refrigeration are mainly of rare earth garnet Gd3Ga5O12(GGG) and Dy3Al5O12(DAG) single crystal. Low-temperature magnetic refrigerating machines made from GGG or DAG are in the magnetic cold circulating type of carnot, and the initial cooling temperature is 16K and 20K respectively.

Low temperature magnetic refrigeration device has the unique advantages, such as miniaturization and high efficiency are widely used in low temperature physics, magnetic resonance imaging, particle accelerators, space technology, infrared detection and microwave receiver, and other fields, some special purpose electronic system in low temperature environment, the reliability and sensitivity to significantly improve.

Magnetic refrigeration is the use of harmless, no environmental pollution of the rare earth materials as refrigerating agent, if replace the current use of freon refrigerant freezers, refrigerators, freezers and air conditioner etc., can eliminate the production and use of class freon refrigerant caused by the destruction of the environment pollution and atmospheric ozone layer, which can protect the human survival environment, has significant environmental and social benefits.

Signed in 1987, more than 80 countries take part in the Montreal protocol on ozone depleting substances regulations, in order to prevent the production and use of chlorine fluorine carbon compounds caused by the atmospheric ozone layer destruction, by 2000 the world will be restricted and prohibited the use of freon refrigerants, in June 1991 in our country to join the international conventions and regulations, by 2010 China will ban the production and use freon fluorine chlorine fluorine carbon and h ydrogen chloride, such as carbon compounds.

Therefore, it is necessary to accelerate the development of innocuous new refrigerants or other types of refrigeration technologies that do not use freon refrigerants. To date, in the research and development of this area, magnetic refrigeration is found to be one of the methods of cooling efficiency, low energy consumption and no pollution. From the current room temperature magnetic refrigeration technology research progress to see in the United States, in three to five years, room temperature magnetic refrigeration technology is likely to get in the car air conditioning system after practical application, and the further development of household air conditioner and refrigerator device such as a magnetic refrigeration.

The refrigeration materials used in magnetic refrigeration are basically alloys or compounds of rare earth metals, especially at room temperature magnetic refrigeration, which are almost entirely used in rare earth metals Gd or Gd base alloys.

Current, magnetic refrigeration materials, technology and equipment research and development, the United States and Japan in the leading level, the developed countries are magnetic refrigeration technology research and development as the end of the century at the beginning of the 21st century's key research projects, has invested large amounts of money, manpower and material resources, the competition is very intense, all want to beat the occupation of the high and new technology.